Volcanoes formed many of the Indonesian islands in Southeast Asia. Sumatra is unique even among its other Indonesian coffee-growing islands and areas. Sumatra, being the second largest island off the coast of Indonesia, is only one of many islands that support the coffee epidemic along with Sulawesi and Java being the other main contributors. As a whole, Indonesia is the fourth-largest coffee-producing country in the world.

The mountainous geography along with the rich soil cultivated from the eruptions make Indonesia the perfect place to grow coffee beans! Roughly 15% of all the coffee grown in Indonesia is Arabica – like the Sumatra Mandheling coffee bean – which meets the standards of gourmet quality coffee. The other 85% is the Robusta species, a commonly used coffee for commercial blending. Coffee grows best in cooler tropical temperatures a few hundred meters above sea level. The rolling hills north of Lampung are ideal for Robusta varieties.  Coffee has been grown here for generations, and many farms are filled with coffee bushes more than a half-century old.

Sumatran’s Unique Characteristics

Sumatran coffees have long been distinct for their earthy, savory, somewhat vegetal or herbaceous characteristics. Partly contributed by the climate and the mix of varieties grown, but also due to a specific post-harvest processing style called Wet-Hulling. This unique style of handling and drying the bean is largely responsible for Sumatran coffees’ unmistakable flavor characteristics, but also their normally greenish-blue hue. It’s known locally as Giling Basah and gives much of the unique qualities to these coffees. The unique method also creates the trademark flavor profile of low acidity and a richness that lingers on the back of the palate while giving the green, unroasted beans a dark color.

The Wet-Hulled process was developed specifically to speed up drying and efficiency in a rainy climate that clouds most of the year.  In this process, coffee farmers will typically harvest their coffee cherry and “depulp” it by hand at their farm or home. The skinned beans are bagged and left to ferment overnight. Then it’s brought either to a coffee marketplace or directly to a “collector,” or collection point, where the beans are purchased at anywhere from 30–50% moisture, with their remaining fruit or mucilage still partially intact. The coffee is then combined and hulled (has its parchment removed) while it is still in this high-moisture state. Removing the parchment layer allows the coffee to dry much faster on patios or tarps even in the humid conditions. The coffee is then dried to the more commonly 11–13% moisture in order to be prepared for export. Sumatra has a wet climate which is great for growing coffee; however, it makes for processing challenges. The wet hulling leaves the coffee’s moisture well above the 11% for a long time usually, until it’s exported. This is where the uniqueness comes from.

While Sumatran coffees are typically characterized by their full bodies and low acidity, the aromas feature more earthy, spicy, wild, and mossy tones. Some might say it taste like wild mushrooms.

Why Sumatran coffee is roasted dark

There is a high variance in characteristics partially from the multi-stage processing method and using homemade hulling machines, so to counteract, the coffee is usually roasted dark. This builds on their body and adds a roast-induced richness to the beans.